Abstract

Background: Cognitive impairments are well-established features of schizophrenia, but there is ongoing debate about the nature and degree of cognitive impairment in patients with schizoaffective disorder and bipolar disorder. We hypothesized that there is a spectrum of increasing impairment from bipolar disorder to schizoaffective disorder bipolar type, to schizoaffective disorder depressive type and schizophrenia.

Limitations: There were fewer participants with schizoaffective disorder and bipolar disorder than schizophrenia. Despite this, our analyses were robust to differences in group sizes, and we were able to detect differences between groups.

Acknowledgments: This work was supported by a Medical Research Council (MRC) PhD studentship to A. Lynham. The work at Cardiff University was funded by MRC Centre (MR/L010305/1) and Program Grant (G0500509). The authors thank Sophie Bishop for her assistance with data collection and participant recruitment. The authors also thank the participants and clinicians who took part in the CoMPaSS study.

Affiliations: From the MRC Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, UK (Lynham, Hubbard, Hamshere, Legge, Owen, Jones, Walters); and the College of Biomedical and Life Sciences, Cardiff University, Cardiff, UK (Tansey).

Competing interests: None declared.

Contributors: A. Lynham, M. Owen and J. Walters designed the study. A. Lynham, S. Legge and J. Walters acquired the data, which A. Lynham, L. Hubbard, K. Tansey, M. Hamshere, S. Legge, I. Jones and J. Walters analyzed. A. Lynham, M. Hamshere, M. Owen, I. Jones and J. Walters wrote the article, which all authors critically reviewed. All authors approved the final version to be published and can certify that no other individuals not listed as authors have made substantial contributions to the paper.